- Published: Monday, 18 July 2016 08:13
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Cheetham Salt is a responsible land manager of over 20,000 ha of often very unique and sensitive land including internationally recognised coastal wetlands. Solar salt ponds attract large numbers of birds and animals. Once established they form an important feeding and roosting area for migratory birds. The ponds themselves are teeming with aquatic life and demonstrate a variety of ecosystems functioning at different salinities.
Cheetham Salt has been active in the control of salinity in Australia for over the past 20 years. Cheetham understands the impact of salinity and has worked extensively with environment protection agencies and key specialists to develop processes to recover the salt in some waste streams. By doing this, Cheetham Salt will reduce the amount of salt being sent to land fills or discharged to waterways.
To optimise the environmental performance Cheetham Salt has expanded its comprehensive management systems to include the requirements set out in ISO 14001. Committed to improving the environmental management of our business, we believe that responsible practices is vital to long term growth to not only meet our customers’ need but also of generations to come.
Cheetham Salt is constantly reviewing our operations to reduce energy use in the business. As the largest domestic supplier of value added solar salt in Australia, Cheetham produces salt using the sun to evaporate water rather than relying on energy intensive machinery.
Cheetham Salt continues to look for opportunities to reduce our water usage and reducing potable water use has been the focus for most sites. All sites are now monitoring and tracking their water consumption. Many have formal water management plans that have been lodged with local/state authorities. Some of the initiatives being used or investigated are: the collection, treatment and use/reuse of rainwater, storm water run-off and boiler blowdown.
Cheetham Salt is committed to minimizing the impact our business has on the environment with methods that are socially responsible, scientifically based and economically sound. We continue to reduce waste through improved recycling systems in all our manufacturing sites by diverting as much waste as possible into recycling streams.
This aerial picture is of the salt production ponds at the Sea Lake facility in Victoria. The pink colour of the ponds is result of Halophiles that are microorganisms which require high salt concentrations to grow.
Salt fields provide important ecosystems for a variety of flora and fauna. A number of the Cheetham sites contain birds or plants of State, National or International significance. At the Bajool site in Queensland, there is a population of the Capricorn Yellow Chat which is listed as Critically Endangered under the Commonwealth Environment and Biodiversity Conservation Act 1999 (EPBC Act). Work being supported by the site has shown that the local population of these birds is larger than originally thought. The Price site in South Australia is listed as a site of International Significance for Shorebirds.
Each of our sites has an environmental licence to operate. These are issued by the Department responsible for the environmental protection of the states in which Cheetham Salt operates. Cheetham Salt is vigilant of its obligations contained within each of the Environmental licences and complies with the licences.
Lake Tyrrell is a large ephemeral salt lake, the level of which is controlled by climate and groundwater. Up to a metre of water fills the basin during the wetter and cooler winter season, but evaporates during the summer, precipitating up to 10 cm of halite. Each year essentially the same pool of ions is redissolved by this annual freshening. The small percentage of gypsum precipated (< 2%) in the surface salt crust reflects the low calcium content of the brine which, in turn, is a function of the negligible net discharge of calcium from the groundwater system. The small influx of fine‐grained clastic sediment to the lake floor comes from surface runoff, wind, and reworking of older sediment from the shoreline.
The Lake Tyrrell basin lies in a setting in which three different groundwater types, identified by distinct salinities, interact with surface waters. A refluxing cycle that goes from discharging groundwater at the basin margin, to surface evaporation on the lake floor, to recharge through the floor of the lake, controls the major chemical characteristics of the basin. In this process, salts are leached downward from the lake floor to join a brine pool below the lake. This provides an outlet from the lake, especially under conditions that have been both drier and wetter than those of today. Enhanced discharge occurs under drier conditions, when the enclosing regional groundwater divide is lowered, whereas a rise in lake level increases the hydraulic head over that of the sub‐surface brine and promotes an increase in brine loss from the lake.
Sulphate‐reducing bacteria in a zone of black sulphide‐rich mud beneath the salt crust help prevent gypsum from being incorporated into the recent sedimentary record. However, below the upper 5 to 10 cm zone of bacterial activity, discoidal gypsum is being precipitated within the mud from the groundwater. These crystals have grown by displacing the mud and typically “float” in a clay matrix; in some zones, they form concentrations exceeding 50% of the sediment. The occasional laminae of more prismatic gypsum that occur within the upper metre of mud have crystallised from surface brines. The scarcity of these comparatively pure prismatic‐crystal concentrations probably is a function of unfavourable chemical conditions in the lake brine and of the role that sulphate‐reducing bacteria have played.
(James T. Tellera, J. M. Bowlerb & P. G. Macumberc ;Modern sedimentation and hydrology in Lake Tyrrell, Victoria pages 159-175 Journal of the Geological Society of Australia Volume 29, Issue 1-2, 1982 Published online: 01 Aug 2007)
Palaeomagnetic investigations by previous studies have demonstrated that Lake Tyrrell represents a remnant of a Pleistocene mega-lake, Lake Bungunnia. This mega-lake is known to have been relatively fresh, and as such is indicative of generally wetter climatic conditions in southeastern Australia during its existence. The drying of Lake Bungunnia commenced between 0.7 Ma and 1.2 Ma, and signaled the onset of aridity in southeastern Australia. Indications from this and other sites point to multiple cycles of wetting and drying, correlated to global glacial-interglacial cycles; as such, this period represents the greatest environmental transformation of the last 20 million years. However, due to periodic deflation resulting from cyclic wetting and drying of the lakebed, the sediment sequence covering this period at Lake Tyrrell is discontinuous. In addition, extensive oxidation of lakebed sediments occurs during dry phases, and wet phases are characterized by secondary mineral precipitation within existing sequences. These conditions have made conventional proxies for palaeo-environmental reconstruction difficult to apply. Microfossil and pollen preservation is generally poor, and sedimentary textures and mineral content altered in some sequences.
References, and further reading
Bowler JM (1976) Aridity in Australia: Age, Origins and Expression in Aeolian Landforms and Sediments Earth Science Reviews 12: 279-310 Bowler JM, Kotsonis A, Lawrence CR (2006) Environmental Evolution of the Mallee Region, Western Murray Basin Proceedings of the Royal Society of Victoria: 161-210
McLaren S, Wallace MW, Pillans BJ, Gallagher SJ, Miranda JA, Warne MT (2009) Revised stratigraphy of the Blanchetown Clay, Murray Basin: age constraints on the evolution of paleo Lake Bungunnia Australian Journal of Earth Sciences 56: 259-270
Stephenson AE (1986) Lake Bungunnia - A Plio-Pleistocene megalake in southern Australia Palaeogeography, Palaeoclimatology, Palaeoecology 57: 137-156
Zhiseng A, Bowler JM, Opdyke ND, Macumber PG, Firman JB (1986) Palaeomagnetic Stratigraphy of Lake Bungunnia: Plio-Pleistocene Precursor of Aridity in the Murray Basin, Southeastern Australia Palaeogeography, Palaeoclimatology, Palaeoecology 54: 219-239
Lake Tyrrell is the site of the oldest known evidence of human habitation of Victoria and Tasmania. A site on the north of Lake Tyrrell has revealed humans were in the vicinity of the Lake 44000 years BCE, with evidence of large earthen ovens containing stone artefacts and a range of charred bones and shells being found a metre below the ground.
Lake Tyrrell is part of the land of the Boorong clan of the Wergaia Language Group. The Boorong were famous astronomers, with their dreaming stories told in the skies reflected on Lake Tyrrell.
When Europeans settled the Mallee in the mid 1800’s, the area around Lake Tyrrell was settled by William Stanbridge, on his sheep run Tyrrell Downs. William Stanbridge was unique amongst his peers in that he formed close links with the Aboriginal people on his pastoral lease. Around the campfire, he sat and listened to their stories of their astronomy, and recorded them. He later presented these stories to the Philosophical Society in Melbourne in his essay On the Astronomy and Mythology of the Aborigines of Australia in 1857.
The Boorong people’s astronomy reflected their experiences of the flora and fauna around them, including the changing seasons as well as reinforcing important cultural values.
Constellations such as Bunya the possum, located in the Southern Cross, as well as Neilloan the Mallee Fowl (in Lyra) can be seen amongst the masses of stars in the Lake Tyrrell night sky, but the Boorong were unique in their use of dark patches in the sky to tell stories as well. The giant Emu Tchingal is found in what is known in Western astronomy as the coal sack. This was a menacing figure in the narratives of the Boorong and features in several stories.
It is worth spending some time exploring the stories of the Boorong Night Skies while visiting Lake Tyrrell. A copy of William Stanbridge’s essay can be found here.
For more information on the Boorong Night Skies we recommend the following links: